The goal of this proposal is to determine the salivary immune response to selected commensal oral bacteria. The majority of diseases that afflict man are caused by exogenous pathogens. However, the principal oral diseases, dental caries and periodontal disease, are caused be endogenous bacteria that are members of the normal oral flora. Although it can be shown that the salivary immune system recognizes and responds to oral bacteria the extent to which the immune system plays a role in the regulation of the indigenous oral flora is unclear. An understanding of the mechanisms by which host protection against cariogenic and periodontopathic bacteria is mediated is essential in the development of vaccines to control these opportunistically pathogenic commensal bacteria. The bacteria chosen for study are Streptococcus mutants, Actinomyces viscosus and A. naeslundii and Bacteroides intermedius. These bacteria were selected because a) they have been implicated in coronal and root surface caries and periodontal disease and b) they represent genera that are either unique to the mouth or are oral species of general that predominate at other mucosal surfaces of the body. It is proposed to conduct a longitudinal study in infants from birth to age two years. The specific aims of this study are to 1) determine the kinetics of colonization of S. muttons, A. viscosus, A. naeslundii and B. intermedius using selective media and fluorescent antibodies, 2) determine the levels and isotypes of salivary antibodies induced in response to the colonization of the selected bacteria using an enzyme-linked immunosorbent assay (ELISA), 3) determine the specificity of antibodies induced in response to colonization by Western blot analysis 4) identify and characterize immunodominant surface antigens by use of monoclonal antibodies and high performance liquid chromatography and 5) correlate the levels, isotypes and specificity of salivary antibodies with colonization of the selected bacteria by comparing ELISA titers and Western blot profiles with the appearance and concentration of the selected bacteria in the mouth.